diff --git a/examples/llm_finetune/nemotron/llama3_3_nemotron_super_49B_squad.yaml b/examples/llm_finetune/nemotron/llama3_3_nemotron_super_49B_squad.yaml
index 0593583c96..42bf48b640 100644
--- a/examples/llm_finetune/nemotron/llama3_3_nemotron_super_49B_squad.yaml
+++ b/examples/llm_finetune/nemotron/llama3_3_nemotron_super_49B_squad.yaml
@@ -121,7 +121,8 @@ ci:
   time: "00:45:00"
   vllm_deploy: true
   checkpoint_robustness:
-    hf_kl_threshold: 5e-3
+    hf_kl_threshold: 2.5e-2
+    resume_loss_threshold: 5e-2
     distributed.tp_size: 8
     tokenizer_name: nvidia/Llama-3_3-Nemotron-Super-49B-v1_5
     hf_device_map_auto: true
diff --git a/nemo_automodel/components/checkpoint/addons.py b/nemo_automodel/components/checkpoint/addons.py
index ac8788f598..7ad8b90a14 100644
--- a/nemo_automodel/components/checkpoint/addons.py
+++ b/nemo_automodel/components/checkpoint/addons.py
@@ -75,12 +75,21 @@ def pre_save(self, **kwargs) -> None:
                     config_name = "config.v5.json"
 
                 _maybe_strip_quantization_config(model_part)
-                with open(os.path.join(hf_metadata_dir, config_name), "w") as f:
+                config_path = os.path.join(hf_metadata_dir, config_name)
+                with open(config_path, "w") as f:
                     if hasattr(model_part.config, "to_json_string"):
                         f.write(model_part.config.to_json_string())
                     else:
                         # Diffusers models use FrozenDict for config instead of PretrainedConfig
                         json.dump(dict(model_part.config), f, indent=2, default=str)
+                if hasattr(model_part.config, "to_json_string"):
+                    # Guarantee ``model_type`` and ``auto_map`` land in the serialized JSON.
+                    # HF's ``PreTrainedConfig.to_json_string`` defaults to ``use_diff=True``,
+                    # which can drop these keys for ``trust_remote_code`` configs (e.g.
+                    # DeciLM / Llama-Nemotron-Super) — causing ``AutoConfig.from_pretrained``
+                    # on the consolidated dir to raise ``Unrecognized model ... Should have
+                    # a 'model_type' key``, breaking checkpoint-robustness reload (Phase 3/4).
+                    _ensure_model_type_and_auto_map(config_path, model_part.config, original_model_path)
 
             # save the generation_config.json file
             if getattr(model_part, "generation_config", None) is not None:
@@ -361,6 +370,66 @@ def _extract_target_modules(model: nn.Module, v4_compatible: bool = False) -> li
     return sorted(final_target_modules)
 
 
+def _ensure_model_type_and_auto_map(config_path: str, config_obj, original_model_path: str | None) -> None:
+    """Ensure the saved ``config.json`` has ``model_type`` and (when applicable) ``auto_map``.
+
+    Context: HF ``PreTrainedConfig.to_json_string`` defaults to ``use_diff=True`` and
+    may omit ``model_type`` or ``auto_map`` for ``trust_remote_code`` configs
+    (e.g. DeciLM / Llama-Nemotron-Super ``model_type='nemotron-nas'``). Without
+    ``model_type`` in ``config.json``, ``AutoConfig.from_pretrained`` on the
+    consolidated directory raises ``Unrecognized model ... Should have a
+    'model_type' key``, breaking checkpoint-robustness reload (Phase 3/4). Without
+    ``auto_map``, HF cannot locate the custom config class even when
+    ``trust_remote_code=True`` is passed.
+    """
+    try:
+        with open(config_path) as f:
+            config_dict = json.load(f)
+    except (OSError, ValueError):
+        config_dict = {}
+
+    # Load the original pretrained config.json once (source of truth for trust_remote_code
+    # models whose ``config_obj`` may have lost ``auto_map`` on the NeMo code path).
+    original: dict = {}
+    if original_model_path and os.path.isdir(original_model_path):
+        src = os.path.join(original_model_path, "config.json")
+        if os.path.isfile(src):
+            try:
+                with open(src) as f:
+                    original = json.load(f)
+            except (OSError, ValueError):
+                original = {}
+
+    changed = False
+
+    if not config_dict.get("model_type"):
+        model_type = (
+            getattr(type(config_obj), "model_type", None)
+            or getattr(config_obj, "model_type", None)
+            or original.get("model_type")
+        )
+        if model_type:
+            config_dict["model_type"] = model_type
+            changed = True
+
+    if not config_dict.get("auto_map"):
+        auto_map = getattr(config_obj, "auto_map", None) or original.get("auto_map")
+        if auto_map:
+            config_dict["auto_map"] = auto_map
+            changed = True
+
+    # Also preserve ``architectures`` from the original if missing; some transformers
+    # versions drop it when serializing custom configs registered via
+    # ``register_for_auto_class``.
+    if not config_dict.get("architectures") and original.get("architectures"):
+        config_dict["architectures"] = original["architectures"]
+        changed = True
+
+    if changed:
+        with open(config_path, "w") as f:
+            json.dump(config_dict, f, indent=2, sort_keys=True)
+
+
 def _maybe_strip_quantization_config(model_part: nn.Module) -> None:
     """Remove ``quantization_config`` from the HF config when no parameters are quantized.